Revelation 8:4 and 5:8 deal with the prayers of the Saints being offered up before the Throne of God. In my mind, that justifies by scripture praying to the saints to pray for us. There are many passgaes in the New Testamnet that tell us to pray for eachother. There is only one Church in both Heaven and Earth. That also explains praying to the Saints to pray for us. Although in Heaven they are still part of the Church and in the presence of God. That brings us back to Revelation and their prayers being offered up to God. The Blessed Virgin to me is all of our Mothers and the first Saint. Who better to pray to then the Mother of Christ who is our Mother too. Jesus said on the cross to the disciple that he loved, behold your Mother!